U.S. patent application number 10/730689 was filed with the patent office on 2004-06-24 for fully implantable miniature neurostimulator for spinal nerve root stimulation as a therapy for angina and peripheral vascular disease.
Invention is credited to McGivern, James P., Whitehurst, Todd K..
Application Number | 20040122477 10/730689 |
Document ID | / |
Family ID | 32600216 |
Filed Date | 2004-06-24 |
United States Patent
Application |
20040122477 |
Kind Code |
A1 |
Whitehurst, Todd K. ; et
al. |
June 24, 2004 |
Fully implantable miniature neurostimulator for spinal nerve root
stimulation as a therapy for angina and peripheral vascular
disease
Abstract
Methods for treatment of peripheral vascular disease and angina
include implantation of a miniature stimulator adjacent at least
one tissue influencing blood circulation. Stimulation sites include
the spinal cord dorsal columns and spinal roots. Stimulation
parameters are tailored to increase coronary blood flow to treat
angina, and/or to increase peripheral blood flow to treat PVD. In
addition, the strength and/or duration of electrical stimulation
required to produce a desired therapeutic effect may be determined
based on a sensed response to and/or need for treatment. Thus, the
stimulation parameters may be adjusted based on a sensed
condition.
Inventors: |
Whitehurst, Todd K.; (Santa
Clarita, CA) ; McGivern, James P.; (Stevenson Ranch,
CA) |
Correspondence
Address: |
ADVANCED BIONICS CORPORATION
12740 SAN FERNANDO ROAD
SYLMAR
CA
91342
US
|
Family ID: |
32600216 |
Appl. No.: |
10/730689 |
Filed: |
December 8, 2003 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60434984 |
Dec 19, 2002 |
|
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|
Current U.S.
Class: |
607/9 ;
607/46 |
Current CPC
Class: |
A61N 1/36071 20130101;
A61N 1/37205 20130101; A61N 1/36146 20130101; A61N 1/36114
20130101 |
Class at
Publication: |
607/009 ;
607/046 |
International
Class: |
A61N 001/18; A61N
001/36 |
Claims
What is claimed is:
1. A method for treating a patient with peripheral vascular disease
(PVD) or angina, comprising: providing a miniature leadless
implantable stimulator with at least one electrode and with a size
and shape suitable for placement entirely within the spinal column;
implanting the stimulator adjacent to at least one tissue
influencing blood circulation, which tissue is at least one of the
spinal roots; providing operating power to the stimulator; using an
external appliance to transmit stimulation parameters to the
stimulator; receiving the stimulation parameters at the stimulator;
generating stimulation pulses in accordance with the stimulation
parameters, which pulses are generated by the stimulator;
delivering stimulation pulses via the stimulator to the at least
one of the spinal roots influencing blood circulation as a
treatment for PVD or angina.
2. The method of claim 1 further comprising delivering stimulation
pulses to at least one of the lumbar dorsal roots, lumbar ventral
roots, sacral dorsal roots, and sacral ventral roots as a treatment
for PVD of at least one lower limb.
3. The method of claim 1 further comprising delivering stimulation
pulses to at least one of the cervical dorsal roots, cervical
ventral roots, thoracic dorsal roots, and thoracic ventral roots as
a treatment for PVD of at least one upper limb.
4. The method of claim 1 further comprising delivering excitatory
stimulation pulses to increase peripheral blood circulation as a
treatment for PVD.
5. The method of claim 1 further comprising delivering stimulation
pulses to at least one of the cervical dorsal roots, cervical
ventral roots, thoracic dorsal roots, and thoracic ventral roots as
a treatment for angina.
6. The method of claim 5 further comprising delivering excitatory
stimulation pulses to increase coronary blood circulation as a
treatment for angina.
7. The method of claim 1 wherein the implantable stimulator further
comprises at least one sensor and the method further comprises
sensing at least one condition of the patient.
8. The method of claim 7 wherein the at least one sensed condition
is used to adjust the stimulation parameters.
9. The method of claim 8 wherein the parameter adjustment is
performed using the at least one external appliance.
10. The method of claim 8 wherein the parameter adjustment is
performed by the implantable stimulator.
11. The method of claim 1 further comprising providing at least one
sensor; using the at least one sensor to sense a physical
condition; and adjusting the stimulation parameters based on the
sensed condition.
12. A method for treating a patient with peripheral vascular
disease (PVD) or angina, comprising: providing a miniature
implantable stimulator with at least one electrode and with a size
and shape suitable for placement of the entire stimulator within
the spinal column; implanting the stimulator adjacent to at least
one tissue influencing blood circulation, which tissue is at least
one of the spinal roots; providing operating power to the
stimulator; using an external appliance to transmit stimulation
parameters to the stimulator; receiving the stimulation parameters
at the stimulator; generating stimulation pulses in accordance with
the stimulation parameters, which pulses are generated by the
stimulator; delivering stimulation pulses via the stimulator to the
at least one of the spinal roots influencing blood circulation as a
treatment for PVD or angina.
13. The method of claim 12 further comprising delivering
stimulation pulses to at least one of the lumbar dorsal roots,
lumbar ventral roots, sacral dorsal roots, and sacral ventral roots
as a treatment for PVD of at least one lower limb.
14. The method of claim 12 further comprising delivering
stimulation pulses to at least one of the cervical dorsal roots,
cervical ventral roots, thoracic dorsal roots, and thoracic ventral
roots as a treatment for PVD of at least one upper limb.
15. The method of claim 12 further comprising delivering excitatory
stimulation pulses to increase peripheral blood circulation as a
treatment for PVD.
16. The method of claim 12 further comprising delivering
stimulation pulses to at least one of the cervical dorsal roots,
cervical ventral roots, thoracic dorsal roots, and thoracic ventral
roots as a treatment for angina.
17. The method of claim 16 further comprising delivering excitatory
stimulation pulses to increase coronary blood circulation as a
treatment for angina.
18. The method of claim 12 wherein the implantable stimulator
further comprises at least one sensor and the method further
comprises sensing at least one condition of the patient.
19. The method of claim 18 wherein the at least one sensed
condition is used to adjust the stimulation parameters.
20. The method of claim 12 further comprising providing at least
one sensor; using the at least one sensor to sense a physical
condition; and adjusting the stimulation parameters based on the
sensed condition.
Description
[0001] The present application claims the benefit of U.S.
Provisional Patent Application Serial No. 60/434,984, filed Dec.
19, 2002, which application is incorporated herein by reference in
its entirety.
BACKGROUND OF THE INVENTION
[0002] Peripheral vascular disease (PVD), such as Raynaud's disease
and thromboangiitis obliterans, affects blood vessels, especially
of the extremities. PVD is a common circulation problem in which
the arteries become narrowed or clogged. Thus, PVD is sometimes
called peripheral arterial disease (PAD). The most common cause of
PVD is atherosclerosis (often called "hardening of the arteries").
Atherosclerosis is the build up of a plaque of cholesterol and scar
tissue that clogs the blood vessels.
[0003] PVD affects about one in twenty people over the age of 50,
or 10 million people in the United States. More than half the
people with PVD experience leg pain, numbness or other symptoms,
but only about half of those with symptoms have been diagnosed with
PVD and are seeing a doctor for treatment.
[0004] Angina is a disease marked by spasmodic attacks of intense
suffocating pain. For instance, angina pectoris may be described as
an aching, burning, or squeezing pain, or as a discomfort,
heaviness, or pressure in the chest that occurs when an inadequate
supply of blood reaches the heart muscle. Angina pectoris is
usually felt in the chest, but may also be felt in the left
shoulder, arms, neck, throat, jaw, or back. Angina pectoris is
usually caused by a narrowing or blockage of the coronary arteries
(blood vessels supplying blood to the heart), which is usually the
result of atherosclerosis.
[0005] Estimates are that 6,600,000 people in the United States
suffer from angina. The estimated age-adjusted prevalence of angina
is greater in women than in men. Angina rates in women age 20 and
older are 3.9 percent for non-Hispanic white women, 6.2 percent for
non-Hispanic black women and 5.5 percent for Mexican-American
women. Rates for men in these three groups are 2.6, 3.1 and 4.1
percent, respectively.
[0006] Existing treatments for PVD and angina suffer from a variety
of disadvantages. Currently used medications tend to improve blood
circulation (i.e., oxygen supply) only acutely, if at all.
(Vasodilators can improve blood supply somewhat.) Existing surgical
procedures are invasive, have high morbidity, and/or are often only
temporarily beneficial. What is needed are less invasive systems
and methods to effectively and efficiently deliver electrical
stimulation to appropriate treatment sites to treat angina and PVD,
and relieve patients of their symptoms.
BRIEF SUMMARY OF THE INVENTION
[0007] The invention disclosed and claimed herein provides
treatments for peripheral vascular disease (PVD) and angina and/or
for relieving their symptoms using one or more implantable
microstimulators for delivering electrical stimulation. The present
invention overcomes the shortfalls of all prior art treatment
devices by delivering such electrical stimulation to the spinal
cord or spinal nerve root(s) via a miniature stimulator implanted
entirely in the spinal column via a minimally invasive surgical
procedure.
[0008] The stimulator used with the present invention possesses one
or more of the following properties, among other properties:
[0009] at least one electrode for applying stimulating current to
surrounding tissue;
[0010] electronic and/or mechanical components encapsulated in a
hermetic package made from biocompatible material(s);
[0011] an electrical coil or other means of receiving energy and/or
information inside the package, which receives power and/or data by
inductive or radio-frequency (RF) coupling to a transmitting coil
placed outside the body, thus avoiding the need for electrical
leads to connect devices to a central implanted or external
controller;
[0012] means for receiving and/or transmitting signals via
telemetry;
[0013] means for receiving and/or storing electrical power within
the stimulator; and
[0014] a form factor making the stimulator implantable via a
minimally invasive procedure in a target area in the body.
[0015] A stimulator may operate independently, or in a coordinated
manner with other implanted stimulators, other implanted devices,
and/or with devices external to a patient's body. For instance, a
stimulator may incorporate means of sensing a patient's condition,
e.g., a means for sensing PVD. Sensed information may be used to
control the electrical stimulation parameters in a closed loop
manner. The sensing and stimulating means may be incorporated into
a single stimulator, or a sensing means may communicate sensed
information to at least one stimulator with stimulating means.
[0016] For most patients, a continuous or intermittent stimulation
throughout the day is needed to provide an adequate amount of
treatment. These patients may best utilize a stimulator that has a
self-contained power source sufficient to deliver repeated pulses
for at least several days and that can be recharged repeatedly, if
necessary. In accordance with the teachings of the present
invention, the use of a stimulator with a rechargeable battery thus
provides these patients the portability needed to free the patient
from reliance on RF power delivery. Alternatively, the power source
may be a primary battery that may last several years.
[0017] For purposes of this patent application, it is sufficient to
note that RF controlled stimulators receive power and control
signals from an extra corporeal antenna coil via inductive coupling
of a modulated RF field. Battery-operated stimulators incorporate a
power source within the device itself but rely on RF control,
inductive linking, or the like to program stimulus sequences and,
if a rechargeable/replenishable power source is used, to
recharge/replenish the power source, when needed. In accordance
with the present invention, each implanted stimulator may be
commanded to produce an electrical pulse of a prescribed magnitude
and duration and at a repetition rate sufficient to treat the
targeted tissue.
[0018] For instance, stimulation may be initiated by start and stop
commands from a patient-governed control switch or controller,
which may be handheld, containing a microprocessor and appropriate
nonvolatile memory, such as electronically erasable programmable
read-only-memory (EEPROM). The controller may control the
implantable stimulator by any of various means. For instance, the
stimulator may sense the proximity of a permanent magnet located in
the controller, or may sense RF transmissions from the
controller.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The above and other aspects of the present invention will be
more apparent from the following more particular description
thereof, presented in conjunction with the following drawings
wherein:
[0020] FIG. 1 illustrates the relation of spinal nerve roots to
vertebrae;
[0021] FIG. 2A depicts nerve pathways in and near the thoracic
spinal cord;
[0022] FIG. 2B illustrates the principal fiber tracts of the spinal
cord;
[0023] FIG. 3 depicts a section through a vertebra;
[0024] FIG. 4 illustrates an exemplary embodiment of a stimulation
system of the present invention;
[0025] FIG. 5 illustrates exemplary external components of the
invention; and
[0026] FIG. 6 depicts a system of implantable devices that
communicate with each other and/or with external
control/programming devices.
[0027] Corresponding reference characters indicate corresponding
components throughout the several views of the drawings.
DETAILED DESCRIPTION OF THE INVENTION
[0028] The following description is of the best mode presently
contemplated for carrying out the invention. This description is
not to be taken in a limiting sense, but is made merely for the
purpose of describing the general principles of the invention. The
scope of the invention should be determined with reference to the
claims.
[0029] As stated above, the relation of spinal nerve roots to
vertebrae is illustrated in FIG. 1. FIG. 2A depicts nerve pathways
in and near the thoracic part of the spinal cord. FIG. 2B
illustrates the principal fiber tracts of the spinal cord, and FIG.
3 depicts a section through a vertebra.
[0030] Spinal Cord Stimulation (SCS) for Angina Pectoris and
Peripheral Vascular Disease (PVD)
[0031] The gate theory of pain proposed by Meizack and Wall in 1965
[see Meizack R, Wall P D. "Pain mechanisms: a new theory." Science
1965; 150:971-9] led to the first spinal cord stimulator being
implanted by Norman Shealy in 1967 for cancer pain. Use of SCS in
angina was reported in 1984 as a chance finding in a patient who
had a stimulator for another reason. [See Sandric, et al. "Clinical
and electrocardiographic improvement of ischemic heart disease
after spinal cord stimulation." Acta Neurochir Suppl 1984;
33:543-6.] SCS systems were first specifically implanted for
intractable angina in Australia in 1987. Since then, there have
been over 70 publications on SCS in refractory angina. These
studies have confirmed improvement in quality of life of these
patients, fewer ischemic episodes, and reduced frequency of
hospital admissions. Moreover, these effects are long-lasting and
are obtained at negligible risk.
[0032] Clinicians are generally concerned about the potential risks
of masking myocardial ischemia with SCS. Studies have demonstrated
that SCS decreases lactate production with pacing and total
ischemic burden, without an increase in silent ischemia. In a study
of fifty patients with coronary artery disease and severe
intractable angina treated with SCS for 1-57 months, Andersen, et
al. found that SCS does not mask the pain of an acute Ml. [See
Andersen, et al. "Does pain relief with spinal cord stimulation for
angina conceal myocardial infarction?" British Heart Journal 1994;
71:419-421.] It has also been found that mortality rates in
patients with SCS systems are similar to those of the general
population of patients with coronary artery disease.
[0033] SCS has been demonstrated to promote local blood flow and
ischemic ulcer healing in patients with peripheral vascular
disease. Positron emission tomography (PET) has shown a more
homogenous pattern of coronary flow following SCS in patients with
myocardial ischemia but no increase in total flow. This
redistribution of flow to areas that were previously ischemic may
explain the increase in exercise capacity prior to the inevitable
onset of angina. To date, there has been no proof of an increase in
coronary flow velocity when patients undergo pacing stress with
SCS. [See Norrsell, et al. "Effects of spinal cord stimulation on
coronary blood flow velocity." Coronary Artery Disease 1998;
9:273-8.]
[0034] It has been proposed that SCS may alter
sympathetic/parasympathetic balance, but no change in heart rate
variability has been shown in a group of post-SCS patients. [See
Hautvast, et al. "Effect of spinal cord stimulation on heart rate
variability and myocardial ischemia in patients with chronic
intractable angina pectoris--a prospective ambulatory
electrocardiographic study." Clinical Cardiology 1998; 21:33-8.]
However, a decrease in resting heart rate and features suggestive
of a functional sympathectomy were found in 25 SCS patients without
coronary disease. [See Meglio, et al. "Spinal cord stimulation
affects the central mechanisms of regulation of heart rate."
Applied Neurophysiology 1986; 49:139-146.] Cerebral PET scanning of
patients with an SCS system demonstrated changes in blood flow in
areas that are known to be related to pain perception in angina.
[See Hautvast, et al. "Relative changes in regional cerebral blood
flow during spinal cord stimulation in patients with refractory
angina pectoris." European Journal of Neuroscience 1997; 9:1178-83,
and Rosen, et al. "Central nervous pathways mediating angina
pectoris." Lancet 1994; 344:147-150.]
[0035] SCS improves microcirculatory blood flow, relieves diabetic
neuropathic and ischemic pain and reduces the amputation rate in
patients with severe peripheral arterial occlusive disease [Huber,
1996; Petrakis, 2000]. In order to evaluate whether transcutaneous
oxygen tension (TcPO.sub.2) measurements can be used as a specific
prognostic parameter in the assessment of suitability for permanent
device implantation in a prospective controlled study on diabetic
patients with peripheral arterial occlusive disease, [Petrakis,
2000] implanted 60 patients (39 men, 21 women; mean age: 60 years;
range: 46-75) with an SCS system for severe peripheral vascular
disease, after failed conservative or surgical treatment. The
primary pathology was diabetic vascular disease. Pedal TcPO.sub.2
was assessed on the dorsum of the foot, and ankle, and toe pressure
Doppler measurements were performed before, two weeks, and four
weeks after implantation.
[0036] Pain relief of over 75% and limb salvage were achieved in 35
diabetic patients, while in 12 a partial success with pain relief
over 50% and limb salvage for at least 6 months were obtained. In
13 patients the method failed and the affected limbs were
amputated. Clinical improvement and SCS success were associated
with increases of TcPO.sub.2 within the first two weeks after
implantation (temporary period). Limb salvage was achieved with
significant increase of TcPO.sub.2 within the first two weeks of
the testing period unrelated to the stage of the disease and the
initial TcPO.sub.2 value. TcPO.sub.2 changes were related to the
presence of adequate paresthesias and warmth in the painful area
during the trial period. The systolic ankle/brachial blood pressure
index (ABI) and toe pressure did not change under stimulation.
[Petrakis, 2000] concluded that a two-week testing period should be
performed in all diabetic patients treated with spinal cord
stimulation for peripheral arterial occlusive disease to identify
the candidates for permanent implantation. Only diabetic patients
with significant increases of TcPO.sub.2 and clinical improvement
during the test period should be considered for permanent
implantation and not merely all patients with pain relief.
[0037] SCS versus Coronary Artery Bypass Graft (CABG) Surgery for
Angina Pectoris
[0038] In 1998, Mannheimer, et al. compared SCS to coronary artery
bypass graft (CABG) surgery in 104 high-risk patients who were
undergoing intervention for symptomatic reasons only and who had an
expected increased risk of surgical complications. [See Mannheimer,
et al. "Electrical stimulation versus coronary artery bypass
surgery in severe angina pectoris. The ESBY study." Circulation
1998; 97:1157-63.] The patients were assessed with respect to
symptoms, exercise capacity, ischemic ECG changes during exercise,
rate-pressure product, mortality, and cardiovascular morbidity
before and six months after the operation. The study found that
both groups had approximately the same significant decrease in
frequency of angina attacks as well as approximately the same
significant decrease in the use of short-acting nitrates. The
primary aim of both treatments is to improve quality of life by
reducing symptoms. In this regard, both SCS and CABG produced
similar benefits. CABG produced an additional improvement in
ischemia on exercise testing at six months. Eight total deaths
occurred during the follow-up period: seven total in the CABG group
(four perioperative) and one in the SCS group. Cerebrovascular
morbidity was also lower in the SCS group. (Most patients lose
approximately ten IQ points as a result of CABG surgery.)
[0039] In a retrospective analysis of 19 patients implanted with
SCS systems between 1987 and 1997, Murray, et al. found that the
annual admission rate after CABG surgery was 0.97 per patient per
year, compared with 0.27 after SCS. [See Murray, et al. "Spinal
cord stimulation significantly decreases the need for acute
hospital admission for chest pain in patients with refractory
angina pectoris." Heart 1999 July; 82(1):89-92.] The mean hospital
time per patient per year after CABG was 8.3 days versus 2.5 days
after SCS. No unexplained ECG changes were observed during
follow-up, and SCS patients presented with unstable angina and
acute Ml in the usual way. The study concludes that SCS effectively
prevents hospital admissions in patients with refractory angina
without masking serious ischemic symptoms or leading to silent
infarction.
[0040] SCS Electrode Location and Stimulation Parameters
[0041] The electrodes for SCS for angina pectoris are typically
implanted in the epidural space of the low cervical and high
thoracic spinal segments, i.e., C7, T1, and T2. The stimulation
voltage employed ranges from 0.7 to 9.5 volts (mean 4.2-4.5 volts),
with an impedance range from 560 to 1667 .OMEGA. (mean 821-920
.OMEGA.). The stimulation frequency is typically set to 85 pps,
although some studies have used frequencies as low as 20 pps with
some efficacy. The pulse width typically used is 210 .mu.sec.
Intermittent stimulation is generally used. Typically the device is
activated episodically by the patient, in response to anginal pain;
studies have found the device active only 10-15% of a given week.
[See, e.g., DeJongste, et al. "Stimulation characteristics,
complications, and efficacy of spinal cord stimulation systems in
patients with refractory angina: a prospective feasibility study."
Pacing and Clinical Electrophysiology 1994 November; 17(11 Pt
1):1751-60, and Jessurun, et al. "Longevity and costs of spinal
cord stimulation systems in patients with refractory angina
pectoris." Third Annual Symposium on Pacing Leads, Ferrara, Italy,
Sep. 11-13, 1997.]
[0042] Transmyocardial Revascu Larization Surgery
[0043] Transmyocardial revascularization (TMR) is a procedure
designed to relieve severe angina in patients who are not
candidates for bypass surgery or angioplasty. During TMR, a surgeon
uses a laser to drill a series of holes from the outside of the
heart into the heart's pumping chamber. Twenty to forty 1 mm laser
channels are created during the procedure. Bleeding from the
channels stops after a few minutes of pressure from the surgeon's
finger. In some patients TMR is combined with bypass surgery. How
TMR reduces angina still isn't fully understood. The laser may
stimulate new blood vessels to grow (angiogenesis). It may destroy
nerve fibers to the heart, making patients unable to feel their
chest pain. In some cases, the channels may remain open, which
would let oxygen-rich blood from the pumping chamber flow into the
channel and then into the heart muscle.
[0044] TMR is FDA approved for use in patients with severe angina
who have no other treatment options. It has also produced early
promising results in three large multi-center clinical trials. The
angina of 80-90 percent of patients who had this procedure has
significantly improved (at least 50 percent) through one year after
surgery. There's still limited follow-up data as to how long this
procedure might last, however.
[0045] Limitations of traditional SCS systems include the bulky
implantable pulse generator (IPG), limited life of an IPG with a
primary battery, and the inconvenience of an RF powered system,
among other limitations. Also, the procedure for implanting a
traditional SCS system involves major surgery, with multiple
incisions, local and general anesthetic, the risks of infection and
other complications, and lengthy recovery time associated
therewith.
[0046] This invention provides a means for chronically stimulating
the spinal cord or spinal nerve root(s) with a miniature
implantable neurostimulator that can be implanted with a minimal
surgical procedure. According to the present invention, a miniature
implantable neurostimulator, such as a bionic neuron (i.e.,
BION.RTM.) may be implanted via a minimal surgical procedure (e.g.,
via a small incision and through a cannula, endoscopically,
laparoscopically) in the spinal cord or in the spinal column
adjacent to a spinal nerve root to treat angina and/or PVD and/or
the symptoms thereof. For example, the spinal nerve roots 110 and
111 lie within the spinal column, and a miniature implantable
neurostimulator may be placed in the spinal column for stimulation
of spinal root(s) 110 and/or 111. A more complicated surgical
procedure, such as a laminectomy, may be required for sufficient
access to a targeted nerve fiber(s), or for fixing the
neurostimulator in place.
[0047] As indicated above, the present invention is directed to
treating PVD and angina using one or more small, implantable
neurostimulators, referred to herein as "microstimulators". The
microstimulators of the present invention are preferably similar to
or of the type referred to as Bionic Neuron (also referred to as a
BION.RTM. microstimulator) devices. The following documents
describe various details associated with the manufacture,
operation, and use of BION implantable microstimulators, and are
all incorporated herein by reference:
1 Application/ Patent/ Filing/Publi- Publication No. cation Date
Title U.S. Pat. No. Issued Implantable Microstimulator 5,193,539
Mar. 16, 1993 U.S. Pat. No. Issued Structure and Method of
5,193,540 Mar. 16, 1993 Manufacture of an Implant- able
Microstimulator U.S. Pat. No. Issued Implantable Device Having
5,312,439 May 17, 1994 an Electrolytic Storage Electrode PCT
Publication published Battery-Powered Patient WO 98/37926 Sep. 3,
1998 Implantable Device PCT Publication published System of
Implantable De- WO 98/43700 Oct. 8, 1998 vices For Monitoring
and/or Affecting Body Parameters PCT Publication published System
of Implantable De- WO 98/43701 Oct. 8, 1998 vices For Monitoring
and/or Affecting Body Parameters U.S. Pat. No. Issued Improved
Implantable Micro- 6,051,017 Apr. 18, 2000 stimulator and Systems
Employing Same published Micromodular Implants to September 1997
Provide Electrical Stimu- lation of Paralyzed Muscles and Limbs, by
Cameron, et al., published in IEEE Trans- actions on Biomedical
Engi- neering, Vol. 44, No. 9, pages 781-790.
[0048] To treat angina pectoris, for example, a microminiature
stimulator 150, such as a BION microstimulator, illustrated, e.g.,
in FIGS. 2B and 4, may be implanted adjacent to the cervical and/or
thoracic spinal cord dorsal column(s). As another example, to treat
PVD of the lower limb(s), a microstimulator 150 may be implanted
adjacent the lumbar and/or sacral spinal cord dorsal column(s).
[0049] Based on the gate control theory described earlier,
stimulating fast-conducting, larger diameter nerve fibers will
block, or gate, the slower pain signals from reaching the brain.
The somatic sensory fibers responsible for touch, pressure, and
position sense are carried through relatively large diameter nerve
fibers (i.e., A-.alpha. and/or A-.beta. fibers), while smaller
diameter nerve fibers (e.g., A-.delta. and/or C fibers) carry pain
signals. As such, angina and/or PVD may be treated with stimulation
additionally or alternatively applied to the larger diameter nerve
fibers, which larger diameter fibers have a relatively lower
threshold of activation than smaller diameter fibers. Excitatory
stimulation of relatively low frequency (e.g., less than about
50-100 Hz) and/or relatively low amplitude (e.g., less than about
15 mA) stimulation is likely to lead to the activation of these
relatively large diameter non-nociceptive sensory fibers.
[0050] In accordance with the present invention, a single
microstimulator 150 may be implanted, or two or more
microstimulators may be implanted to achieve greater stimulation of
the targeted tissue, or for a longer period of time. In the example
of FIG. 4, microstimulator device 150 includes a narrow, elongated
case 152 containing electronic circuitry 154 connected to
electrodes 156 and 158, which may pass through the walls of the
case at either end. Alternatively, electrodes 156 and/or 158 may be
built into and/or onto the case and/or arranged on a distal portion
of a lead, as described below. As detailed in the referenced
publications, electrodes 156 and 158 generally comprise a
stimulating electrode (to be placed close to the nerve) and an
indifferent electrode (for completing the circuit). Other
configurations of microstimulator device 150 are possible, as is
evident from the above-referenced publications.
[0051] A preferred implantable microstimulator 150 is sufficiently
small to permit its placement near the structures to be stimulated.
(As used herein, "adjacent" and "near" mean as close as reasonably
possible to target tissue(s), including touching or even being
positioned within the tissue, but in general, may be as far as can
be reached with the stimulation pulses.) As such, case 152 may have
a diameter of about 4-5 mm, or only about 3 mm, or even less than
about 3 mm. In these configurations, case length may be about 25-35
mm, or only about 20-25 mm, or even less than about 20 mm. The
shape of the microstimulator may be determined by the structure of
the desired target, the surrounding area, and the method of
implantation. A thin, elongated cylinder with electrodes at the
ends, as shown in FIG. 4, is one possible configuration, but other
shapes, such as rounded cylinders, spheres, disks, and helical
structures, are possible, as are different configurations of and/or
additional electrodes.
[0052] Microstimulator 150 is preferably implanted with a surgical
insertion tool specially designed for the purpose (see, e.g., U.S.
Pat. No. 6,582,441), or may be placed, for instance, via a small
incision and through a small cannula. Alternatively, device 150 may
be implanted via conventional surgical methods, or may be inserted
using other endoscopic or laparoscopic techniques. A more
complicated surgical procedure may be required for purposes of
fixing the microstimulator in place.
[0053] The external surfaces of stimulator 150 are advantageously
composed of biocompatible materials. To protect the electrical
components inside stimulator 150, at least a portion of case 152 is
hermetically sealed. For instance, stimulator case 152 may be made
of, for instance, glass, ceramic, or other material that provides a
hermetic package that excludes water vapor but permits passage of
electromagnetic fields used to transmit data and/or power. For
additional protection against, e.g., impact, the case may be made
of metal (e.g., titanium) or ceramic, which materials are also,
advantageously, biocompatible. In addition, stimulator 150 may be
configured to be Magnetic Resonance Imaging (MRI) compatible.
Electrodes 156 and 158 may be made of a noble or refractory metal
or compound, such as platinum, iridium, tantalum, titanium,
titanium nitride, niobium, or alloys of any of these, in order to
avoid corrosion or electrolysis, which could damage the surrounding
tissues and the device.
[0054] In some embodiments of the instant invention,
microstimulator 150 comprises at least one, leadless electrode.
However, one, some, or all electrodes may alternatively be located
at the end of short, flexible leads (e.g., see FIG. 5) as described
in U.S. patent application Ser. No. 09/624,130, filed Jul. 24, 2000
(which claims priority to U.S. Provisional Patent Application No.
60/156,980, filed Oct. 1, 1999), which is incorporated herein by
reference in its entirety. Other configurations may also permit
electrical stimulation to be directed more locally to specific
tissue a short distance from the surgical fixation of the bulk of
the implantable stimulator 150, while allowing elements of
stimulator 150 to be located in a more surgically convenient site.
Such configurations minimize the distance traversed and the
surgical planes crossed by the device and any lead(s). In most
embodiments, the leads are no longer than about 150 mm.
[0055] Microstimulator 150 contains, when necessary and/or desired,
electronic circuitry 154 (FIG. 4) for receiving data and/or power
from outside the body by inductive, radio-frequency (RF), or other
electromagnetic coupling. In some embodiments, electronic circuitry
154 includes an inductive coil for receiving and transmitting RF
data and/or power, an integrated circuit (IC) chip for decoding and
storing stimulation parameters and generating stimulation pulses
(either intermittent or continuous), and additional discrete
components required to complete the circuit functions, e.g.
capacitor(s), resistor(s), coil(s), and the like. Circuitry 154 may
dictate, for instance, the amplitude and duration of the electrical
current pulses.
[0056] Microstimulator 150 also includes, when necessary and/or
desired, a programmable memory 160 for storing set(s) of data,
stimulation, and/or control parameters. Among other things, memory
164 may allows stimulation and/or control parameters to be adjusted
to settings that are safe and efficacious with minimal discomfort
for each individual. Specific parameters may provide therapeutic
advantages for different patients or for various types and classes
of angina and/or PVD. For instance, some patients may respond
favorably to intermittent stimulation, while others may require
continuous stimulation for treatment and relief.
[0057] In addition, different parameters may have different effects
on different tissue. Therefore, stimulation and control parameters
may be chosen to target specific neural or other cell populations
and/or to exclude others, or to increase activity in specific
neural or other cell populations and/or to decrease activity in
others. For example, relatively low frequency neurostimulation
(i.e., less than about 50-100 Hz) may have an excitatory effect on
surrounding neural tissue, leading to increased neural activity
("excitatory stimulation"), whereas relatively high frequency
neurostimulation (i.e., greater than about 50-100 Hz) may have an
inhibitory effect, leading to decreased neural activity
("inhibitory stimulation"). As another example, relatively low
levels of stimulation current (typically less than about 15 mA, but
dependent on the distance between electrodes and nerve fibers) are
likely to recruit only relatively large diameter fibers (e.g.,
A-.alpha. and/or A-.beta. fibers), while nociceptive fibers are
typically relatively small diameter fibers (e.g., A-.delta. and/or
C fibers).
[0058] Some embodiments of implantable stimulator 150 also includes
a power source and/or power storage device 162 (FIG. 4). Possible
power options, described in more detail below, include but are not
limited to an external power source coupled to stimulator 150
(e.g., via an RF link), a self-contained power source utilizing any
suitable means of generation or storage of energy (e.g., a primary
battery, a replenishable or rechargeable battery such as a lithium
ion battery, an electrolytic capacitor, a super- or
ultra-capacitor, or the like), and if the self-contained power
source is replenishable or rechargeable, means of replenishing or
recharging the power source (e.g., an RF link, an optical link, a
thermal link, or other energy-coupling link).
[0059] According to certain embodiments of the invention, a
microstimulator operates independently. According to other
embodiments of the invention, a microstimulator operates in a
coordinated manner with other microstimulator(s), other implanted
device(s), and/or other device(s) external to the patient's body.
For instance, a microstimulator may control or operate under the
control of another implanted microstimulator(s), other implanted
device(s), or other device(s) external to the patient's body. A
microstimulator may communicate with other implanted
microstimulators, other implanted devices, and/or devices external
to a patient's body via, e.g., an RF link, an ultrasonic link, a
thermal link, or an optical link. Specifically, a microstimulator
may communicate with an external remote control (e.g., patient
and/or physician programmer) that is capable of sending commands
and/or data to a microstimulator and that is preferably capable of
receiving commands and/or data from a microstimulator.
[0060] In certain embodiments, and as illustrated in FIG. 5, the
patient 170 switches stimulator 150 on and off by use of controller
180, which may be handheld. Implantable stimulator 150 may be
operated by controller 180 by any of other various means, including
sensing the proximity of a permanent magnet located in controller
180, sensing RF transmissions from controller 180, or the like.
[0061] Additional and alternative exemplary external components for
programming and/or providing power to various embodiments of
stimulator 150 are also illustrated in FIG. 5. When communication
with such a stimulator 150 is desired, patient 170 is positioned on
or near external appliance 190, which appliance contains one or
more inductive coils 192 or other means of communication (e.g., RF
transmitter and receiver). External appliance 190 is connected to
or is a part of external circuitry appliance 200 which may receive
power 202 from a conventional power source. External appliance 200
contains manual input means 208, e.g., a keypad, whereby the
patient 170 or a caregiver 212 (e.g., a clinician) may request
changes in stimulation parameters produced during the normal
operation of the implantable stimulator 150. In these embodiments,
manual input means 208 preferably includes various
electro-mechanical switches and/or visual display devices that
provide the patient and/or caregiver with information about the
status and prior programming of the implantable stimulator 150.
[0062] Alternatively or additionally, external electronic appliance
200 is provided with an electronic interface means 216 for
interacting with other computing means 218, such as via serial
interface cable or infrared link to a personal computer or
telephone modem or the like. Such interface means 216 may permit a
clinician to monitor the status of the implant and prescribe new
stimulation parameters from a remote location.
[0063] One or more of the external appliance(s) may be embedded in
a cushion, mattress cover, garment, or the like. Other
possibilities exist, including a strap, patch, or other
structure(s) that may be affixed to the patient's body or clothing.
External appliances may include a package that can be, e.g., worn
on the belt, may include an extension to a transmission coil
affixed, e.g., with a Velcro.RTM. band or an adhesive, or may be
combinations of these or other structures able to perform the
functions described herein.
[0064] In order to help determine the strength and/or duration of
electrical stimulation required to produce the desired therapeutic
effect, in some embodiments, a patient's response to and/or need
for treatment is sensed, e.g., via ECG changes, an oxygen sensor or
a flowmeter in the coronary circulation to detect indicators of
angina. As another example, a microstimulator may incorporate means
for sensing indicators of PVD, such as via an oxygen sensor or
flowmeter in a limb. Sensed information may be used to control the
stimulation parameters of a microstimulator in a closed-loop
manner. According to some embodiments of the invention, the sensing
and stimulating means are both incorporated into a single
microstimulator. Thus, when microstimulator 150 is implanted, for
example, near dorsal column 120, signals from a sensor built into
microstimulator 150 may be used to adjust stimulation parameters.
For instance, with stimulator 150 near dorsal column 120,
stimulation may be initiated or amplitude increased if increased
dorsal column activity is sensed via ENG. In another example, with
stimulator 150 implanted in the spinal column near dorsal root 100,
stimulation may be initiated or amplitude increased if ECG changes
suggestive of angina are sensed.
[0065] According to other embodiments, the sensing means are
incorporated into at least one "microstimulator" (that may or may
not have stimulating means), and the sensed information is
communicated to at least one other microstimulator with stimulating
means. A microstimulator or other sensor may additionally or
alternatively incorporate means of sensing other measures of the
state of the patient, e.g., EMG, acceleration, patient activity,
respiratory rate, medication levels, neurotransmitter levels,
hormone levels, interleukin levels, cytokine levels, lymphokine
levels, chemokine levels, growth factor levels, enzyme levels,
and/or levels of other blood-borne compounds. For instance, one or
more Chemically Sensitive Field-Effect Transistors (CHEMFETs), such
as Enzyme-Selective Field-Effect Transistors (ENFETs) or
Ion-Sensitive Field-Effect Transistors (ISFETs, as are available
from Sentron CMT of Enschede, The Netherlands), may be used.
[0066] Thus, a "microstimulator" dedicated to sensory processes may
communicate with a microstimulator that provides the stimulation
pulses. For instance, a microstimulator, such as a BION.RTM.
manufactured by Advanced Bionics of Sylmar, Calif., may be used to
detect abnormal cardiac electrocardiogram (ECG) events. A BION may
use one of many algorithms for analyzing ECGs. These algorithms can
operating in the frequency domain, time domain or both. They may
employ linear, non-linear, or statistical analysis to categorize
the electrogram as originating from various modes, i.e., normal
sinus rhythms, sinus tachycardia, ventricular tachycardia, and
ventricular fibrillation. In addition, by finding the P, R, and T
waves or analyzing the timing of the relationships and durations of
the P-wave, QRS complex, and T-wave, it is possible to identify
various disease states and make predictive diagnosis about
perfusion of the myocardium. Other abnormalities that may be
monitored include ST segment elevation, T wave peaking or
inversion, among others discussed earlier. See, for instance, U.S.
Pat. No. 5,513,644, titled "Cardiac arrhythmia detection system for
an implantable stimulation device," which is incorporated herein by
reference in its entirety.
[0067] Other methods of determining the required stimulation
include an oxygen or flow sensor in the coronary circulation and/or
in a limb, as well as other methods mentioned herein, and yet
others that will be evident to those of skill in the art upon
review of the present disclosure. The sensed information may be
used to control the electrical and/or control parameters in a
closed-loop manner.
[0068] For instance, in several embodiments of the present
invention, a first and second "stimulator" are provided. The second
"stimulator" periodically (e.g. once per minute) records e.g., ECG,
which it transmits to the first stimulator. Implant circuitry 154
may, if necessary, amplify, filter, process, then transmit these
sensed signals, which may be analog or digital. The first
stimulator uses the sensed information to adjust stimulation
parameters according to an algorithm programmed, e.g., by a
physician. For example, amplitude of stimulation may be initiated
or increased in response to ST segment elevation and/or T wave
inversion. More preferably, one "microstimulator" performs the
sensing, stimulation parameter adjustments, and current generating
functions.
[0069] While a microstimulator may also incorporate means of
sensing angina, PVD, or their symptoms, it may alternatively or
additionally be desirable to use a separate or specialized
implantable device to sense and telemeter physiological
conditions/responses in order to adjust stimulation parameters.
This information may then be transmitted to an external device,
such as external appliance 220, or may be transmitted directly to
implanted stimulator(s) 150. However, in some cases, it may not be
necessary or desired to include a sensing function or device, in
which case stimulation parameters are determined and refined, for
instance, by patient feedback.
[0070] Thus, it is seen that in accordance with the present
invention, one or more external appliances are preferably provided
to interact with microstimulator 150 to accomplish one or more of
the following functions:
[0071] Function 1: If necessary, transmit electrical power from the
external electronic appliance 200 via appliance 190 to the
implantable stimulator 150 in order to power the device and/or
recharge the power source/storage device 162. External electronic
appliance 200 may include an automatic algorithm that adjusts
stimulation parameters automatically whenever the implantable
stimulator(s) 150 is/are recharged.
[0072] Function 2: Transmit data from the external appliance 200
via the external appliance 190 to the implantable stimulator 150 in
order to change the operational parameters (e.g., electrical
stimulation parameters) used by stimulator 150.
[0073] Function 3: Transmit sensed data indicating a need for
treatment or in response to stimulation (e.g., ECG) from
implantable stimulator 150 to external appliance 200 via external
appliance 190.
[0074] Function 4: Transmit data indicating state of the
implantable stimulator 150 (e.g., battery level, stimulation
settings, etc.) to external appliance 200 via external appliance
190.
[0075] By way of example, a treatment modality for PVD may be
carried out according to the following sequence of procedures:
[0076] 1. A stimulator 150 is implanted so its electrodes 156
and/or 158 are adjacent to a lumbar dorsal column 120.
[0077] 2. Using Function 2 described above (i.e., transmitting
data) of external electronic appliance 200 and external appliance
190, implantable stimulator 150 is commanded to produce a series of
excitatory electrical stimulation pulses.
[0078] 3. Set stimulator on/off period to an appropriate setting,
e.g., continuously on.
[0079] 4. After each stimulation pulse, series of pulses, or at
some other predefined interval, any change in dorsal column
activity is sensed (via ENG), preferably by one or more electrodes
156 and 158 of implantable stimulator 150. These responses are
converted to data and telemetered out to external electronic
appliance 200 via Function 3.
[0080] 5. From the response data received at external appliance 200
from the implantable stimulator 150, or from other assessment, the
stimulus threshold for obtaining a reflex response is determined
and is used by a clinician acting directly 212 or by other
computing means 218 to transmit the desired stimulation parameters
to the implantable stimulator 150 in accordance with Function 2.
Alternatively, external appliance 200 makes the proper adjustments
automatically, and transmits the proper stimulation parameters to
stimulator 150. In yet another alternative, stimulator 150 adjusts
stimulation parameters automatically based on the sensed
response.
[0081] 6. When patient 170 desires to invoke an electrical
stimulation to alleviate symptoms (e.g., pain, loss of function,
etc.), patient 170 employs handheld controller 180 to set the
implantable stimulator 150 in a state where it delivers a
prescribed stimulation pattern from a predetermined range of
allowable stimulation patterns.
[0082] 7. Patient 170 employs controller 180 to turn off stimulator
150, if desired.
[0083] 8. Periodically, the patient or caregiver recharges the
power source/storage device 162 of implantable stimulator 150, if
necessary, in accordance with Function 1 described above (i.e.,
transmit electrical power).
[0084] In another example, a treatment modality for angina pectoris
may be carried out according to the following sequence of
procedures:
[0085] 1. A stimulator 150 is implanted in the spinal column so its
electrodes 156 and/or 158 are adjacent to a dorsal root 110 and/or
ventral root 111.
[0086] 2. Using Function 2 described above (i.e., transmitting
data) of external electronic appliance 200 and external appliance
190, implantable stimulator 150 is commanded to produce a series of
excitatory electrical stimulation pulses.
[0087] 3. Set stimulator on/off period to an appropriate setting,
e.g., continuously on.
[0088] 4. After each stimulation pulse, series of pulses, or at
some other predefined interval, any change in ECG suggestive of
angina pectoris is sensed, preferably by one or more electrodes 156
and 158 of implantable stimulator 150. These responses are
converted to data and telemetered out to external electronic
appliance 200 via Function 3.
[0089] 5. From the response data received at external appliance 200
from the implantable stimulator 150, or from other assessment, the
stimulus threshold for obtaining a reflex response is determined
and is used by a clinician acting directly 212 or by other
computing means 218 to transmit the desired stimulation parameters
to the implantable stimulator 150 in accordance with Function 2.
Alternatively, external appliance 200 makes the proper adjustments
automatically, and transmits the proper stimulation parameters to
stimulator 150. In yet another alternative, stimulator 150 adjusts
stimulation parameters automatically based on the sensed
response.
[0090] 6. When patient 170 desires to invoke an electrical
stimulation to alleviate symptoms (e.g., pain, loss of function,
etc.), patient 170 employs handheld controller 180 to set the
implantable stimulator 150 in a state where it delivers a
prescribed stimulation pattern from a predetermined range of
allowable stimulation patterns.
[0091] 7. Patient 170 employs controller 180 to turn off stimulator
150, if desired.
[0092] 8. Periodically, the patient or caregiver recharges the
power source/storage device 162 of implantable stimulator 150, if
necessary, in accordance with Function 1 described above (i.e.,
transmit electrical power).
[0093] For the treatment of any of the various types and classes of
angina and/or PVD, it may be desirable to modify or adjust the
algorithmic functions performed by the implanted and/or external
components, as well as surgical approaches. For example, in some
situations, it may be desirable to employ more than one implantable
stimulator 150, each of which could be separately controlled by
means of a digital address. Multiple channels and/or multiple
patterns of stimulation might thereby be programmed by the
clinician and controlled by the patient in order to, for instance,
deal with complex or multidimensional pain such as may occur as a
result of poor circulation in multiple limbs.
[0094] In some embodiments discussed earlier, microstimulator 150,
or two or more microstimulators, is controlled via closed-loop
operation. A need for and/or response to stimulation is sensed via
microstimulator 150, or by an additional microstimulator (which may
or may not be dedicated to the sensing function), or by another
implanted or external device. If necessary, the sensed information
is transmitted to microstimulator 150. In some cases, the sensing
and stimulating are performed by one stimulator. In some
embodiments, the stimulation parameters used by microstimulator 150
are automatically adjusted based on the sensed information. For
instance, one "microstimulator" may performs the sensing,
stimulation parameter adjustments, and current generating
functions. Thus, the stimulation parameters may be adjusted in a
closed-loop manner to provide stimulation tailored to the need for
and/or response to stimulation.
[0095] For example, as seen in FIG. 6, a first microstimulator 150,
implanted in a first location, provides electrical stimulation to a
first location, e.g., a left upper lumbar spinal cord dorsal
column; a second microstimulator 150' provides electrical
stimulation to a second location, e.g., a right upper lumbar dorsal
column; and a third microstimulator 150" provides electrical
stimulation to a third location, e.g., a left lower lumbar dorsal
column. As mentioned earlier, the implanted devices may operate
independently or may operate in a coordinated manner with other
similar implanted devices, other implanted devices, or other
devices external to the patient's body, as shown by the control
lines 222, 223 and 224 in FIG. 6. That is, in accordance with
certain embodiments of the invention, an external controller 220
controls the operation of one or more of the implanted
microstimulators 150, 150' and 150".
[0096] According to various embodiments of the invention, an
implanted device, e.g., microstimulator 150, may control or operate
under the control of another implanted device(s), e.g.,
microstimulator 150' and/or microstimulator 150". That is, a device
made in accordance with the invention may communicate with other
implanted stimulators, other implanted devices, and/or devices
external to a patient's body, e.g., via an RF link, an ultrasonic
link, a thermal link, an optical link, or the like. Specifically,
as illustrated in FIG. 6, microstimulator 150, 150', and/or 150",
made in accordance with the invention, may communicate with an
external remote control (e.g., patient and/or physician programmer
220 and/or the like) that is capable of sending commands and/or
data to implanted devices and may also be capable of receiving
commands and/or data from implanted devices.
[0097] Microstimulators made in accordance with the invention
further incorporate, in some embodiments, first sensing means 228
for sensing therapeutic effects, clinical variables, or other
indicators of the state of the patient, such as perfusion (e.g.,
limb perfusion) via a doppler flowmeter, or sympathetic trunk
activity via ENG. The stimulators additionally or alternatively
incorporate second means 229 for sensing, e.g., levels and/or
changes in catecholamines and/or other markers of the potential for
pain. The stimulators additionally or alternatively incorporate
third means 230 for sensing electrical current levels and/or
waveforms supplied by another source of electrical energy. Sensed
information may then be used to control the parameters of the
stimulator(s) in a closed loop manner, as shown by control lines
225, 226, and 227. Thus, the sensing means may be incorporated into
a device that also includes electrical stimulation means, or the
sensing means (that may or may not have stimulating means), may
communicate the sensed information to another device(s) with
stimulating means.
[0098] Thus, for the treatment of angina and/or the symptoms
thereof, according to the present invention, the target site(s) of
electrical stimulation include the cervical and/or thoracic spinal
cord dorsal column(s) 120, and/or the cervical and/or thoracic
spinal root(s). As shown in FIGS. 2A and 2B, dorsal columns 120
include cuneate fasciculus 122 and gracile fasciculus 124. As shown
in FIGS. 2A and 3, the spinal roots lie within the spinal column,
and include dorsal (posterior) root 110 and ventral (anterior) root
111. Such treatment may be targeted to increase coronary blood
circulation as a means to control angina, angina pain, or other
symptoms. Such a result is most likely with excitatory stimulation
(applied at a relatively low frequency, e.g., less than about
100-150 Hz).
[0099] In addition, for the treatment of peripheral vascular
disease (PVD) of the lower limb(s), the target site(s) of
electrical stimulation include the lumbar and/or sacral spinal cord
dorsal column(s) 120 (cuneate fasciculus 122 and/or gracile
fasciculus 124) and/or the lumbar and/or sacral spinal root(s)
(dorsal root 110 and/or ventral root 111). For treatment of
peripheral vascular disease of the upper limb(s), the target
site(s) of electrical stimulation include the cervical and/or
thoracic spinal cord dorsal column(s) 120 (cuneate fasciculus 122
and/or gracile fasciculus 124) and/or the cervical and/or thoracic
spinal root(s) (dorsal root 110 and/or ventral root 111). Such
treatment may be targeted to increase peripheral blood circulation
as a means to control PVD, PVD pain, or other symptoms related to
PVD and its sequelae. Such a result is most likely with excitatory
stimulation (applied at a relatively low frequency, e.g., less than
about 100-150 Hz).
[0100] Furthermore, sensing means described earlier may be used to
orchestrate first the activation of microstimulator(s) targeting
one or more nerve fibers, and then, when appropriate, the
microstimulator(s) targeting nerve fibers in another area and/or by
a different means. Alternatively, this orchestration may be
programmed, and not based on a sensed condition. In yet another
alternative, this coordination may be controlled by the patient via
the patient programmer.
[0101] While the invention herein disclosed has been described by
means of specific embodiments and applications thereof, numerous
modifications and variations could be made thereto by those skilled
in the art without departing from the scope of the invention set
forth in the claims.
* * * * *